The present invention relates to a method of forming a multicolor image and materials for forming the multicolor image to be used therefor. In more detail, it relates to a forming method of a multicolor image on a color proof for proofing the color used for the proof operation in the printing plate-making process.
In the color printing, a material called a color proof for proofing color is used commonly to check the color, tone-reproduction etc. of a finished print in each operation process of plate-making.
For obtaining these materials, (1) a method wherein, prior to transferring each color image onto a desired sheet, each color image is transferred once onto a temporary image-receiving sheet provided with a photopolymerizable image-receiving layer, then they are transferred onto a desired sheet, and further the photopolymerizable image-receiving layer is hardened through the exposure of light on the overall surface (for example, Japanese Unexamined Patent Publication No. Sho 59-97410), (2) a method wherein image layers formed on transferable photosensitive materials are transferred onto an image-receiving sheet material comprising a supporter and an organic high-molecular substance provided thereon, and then the image is retransferred onto a permanent supporter (Japanese Unexamined Patent Publication No. Sho 62-27735), (3) a method wherein image layers formed on transferable photosensitive materials are transferred onto an image-receiving sheet material comprising a supporter, a first layer consisting of a first organic high-molecular substance provided thereon and a second layer consisting of a second organic high-molecular substance provided further thereon, and then the image is retransferred onto a permanent supporter (Japanese Unexamined Patent Publication No. Sho 61-189535), and (4) a method wherein image layers formed on transferable photosensitive materials are transferred onto an image-receiving sheet material having a supporter and a layer of an image-receiving layer consisting of an organic high-molecular substance provided thereon, and then the image layer alone is retransferred onto a permanent supporter (Japanese Unexamined Patent Publications No. Sho 64-52135 and No. Hei 3-21955) are known.
In the methods of (1) and (2), however, the surface having the image formed finally is covered with a layer consisting of an organic high-molecule in all cases, hence the gloss of the image surface obtained is too high, giving an impression different from the image quality after actual printing.
For this reason, for the purpose of adjusting the gloss of the image surface, a method wherein a matted sheet having a roughened surface and the image surface formed on the permanent supporter are superposed and treatments such as pressurizing and heating are given to alter the surface gloss of the image is also used, but there are problems in the runnability that the operation of this method is troublesome by itself, many types of matted sheets are required to achieve the aimed gloss, and the like.
Moreover, the layer covering the image surface and consisting of the organic high-molecule makes the optical dot gain higher than that of the actual print, leading to the tone reproduction different from the print.
Next, with respect to the method (3), this method has such advantages that, when the second layer of said image-receiving sheet is transferred onto the permanent supporter together with an image layer, said layer is buried adapting to the irregularities of the surface of the permanent supporter, thus giving a good adhesion to the permanent supporter, and also, after the supporter of the image-receiving sheet was peeled off, the matting process is not required. But, because of the existence of the layer covering the image surface and consisting of the organic high-molecule similarly, the optical dot gain becomes higher than that of actual print, leading to the tone reproduction different from the print.
On the contrary, in the method (4), the image-receiving sheet having one layer of the image-receiving layer is used, and, when retransferring, the image layer alone is transferred from the image-receiving layer onto the permanent supporter, hence the quality of proof becomes close to the quality of actual print.
In this method, however, when transferring the image layer on the image-receiving sheet onto the permanent supporter such as paper, if the image-receiving layer of the image-receiving sheet and the permanent supporter contact directly, for example, if the image-receiving layer is thick enough to have a cushioning property, then the image layer is buried into the image-receiving layer, tending to directly contact the image-receiving layer with the permanent supporter. In this case, the adhesive force of both is too strong and, when peeling off the image-receiving sheet, the phenomena such as picking takes place, limiting the type of paper usable as a permanent supporter. Moreover, in the transferring operation, some knacks are needed on peeling off the image-receiving sheet finally. These and others have problems in the runnability.
The invention therefore aims at obtaining such a color proof material that the final matting process of the surface of the proof is not required, phenomena such as picking do not take place on peeling off the image-receiving sheet after transferring the image layers on the image-receiving sheet onto the permanent supporter such as paper, special knacks are not needed also on peeling off the image-receiving sheet, and color proof is close to the print with good runnability.